Via getcrafty and it's glitter boards
and this post:

Crocheting with recycled plastic bags!!!!
here are the links,
Plastic Bag Handbag
Crocheted Plastic Bag Links

So who's to say that you couldn't knit with these too. I don't think I'd wear plastic bag craft, like hats or jackets or sweaters...But a tote bag, "don't throw away" Grocery bag, or place mats could be pretty cool.

Oh and you'd have to find a place with some cool colored plastic bags. Safeways plastic bags are brown with red letters. I don't really like that color scheme and that's where we shop usually.

Any other ideas or links to patterns that would work? Any stores w/ pretty plastic bags?